Posts: 1
From:Sioux Falls, SD, USA
Registered: Sep 2005

posted September 07, 2005 09:58 AM               

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Hello, All,
New to this board. Does anyone have a good spread sheet for documenting / tracking barrel and screw ware?

Thanks

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Posts: 31
From:bethesda MD USA
Registered: Sep 2001

posted October 23, 2005 03:52 PM            

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Dear Casey,
Don't worry about wear, worry about what it can and cannot do. Follow output per rpm for a known material over weeks and months, and if that doesn't change, wear isn't affecting pumping capacity.
Wear has been accused of all kinds of extrusion problems, but seldom is there enough evidence to convict.
Once in a while, wear does affect pumping capacity and requires higher rpm for the same output, ALL OTHER THINGS BEING EQUAL. In that case, if you have the HP and the possible higher melt temp doesn't bother you, take the money and run.
If it does, then you may have reason to rebuild the screw. However it's very difficult to rebuild a screw to what it once was -- not because it can't be done, but because there will be lots of suggestions for new screw designs, new metals, etc., some of which do really have merit. So look at a wear problem as something to avoid, consider rebuild as an engineering project, not just a maintenance job, and rebuild only if called for by economic analysis -- remembering that if you don't sell the increased output, running faster doesn't get you very much, and may increase tolerances enough to lose more than you gain.
Hope this helps,
Allan Griff, Consulting Engineer www.griffex.com

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